Bariatric surgery was found to correlate with longer life expectancy than usual care in patients with obesity, according to study data published in the New England Journal of Medicine.

The Swedish Obese Subjects (SOS) study (ClinicalTrials.gov Identifier: NCT01479452) is a prospective study conducted at 25 public surgical departments and 480 primary health care centers in Sweden. From September 1, 1987 and January 31, 2001, the investigators recruited 2010 patients aged 37 to 60 years who underwent bariatric surgery for obesity. Participants in the surgery group underwent banding (18%), vertical banded gastroplasty (69%), or gastric bypass (13%); participants in the control group received conventional obesity treatment.

The study cohort comprised 2007 and 2040 patients in the surgery and control groups, respectively. The mean patient age at enrollment was similar in both cohorts (surgery, 47.2±5.9 vs control, 48.7±6.3 years). The majority of participants with obesity were women (>70% in both groups). The median follow-up for mortality was 24 years (interquartile range [IQR], 22-27) in the surgical group and 22 years (IQR, 21-27) in the control group. The median follow-up was 20 years (IQR, 19-21) in the reference cohort (mean age, 49.5±7.0 years; 53.8% women).

Participants in the SOS reference study, conducted between 1994 and 1999, were used as a population-based reference cohort for the present study. The reference study enrollees (N=1135) were aged 37 to 60 years and were not obese.


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The investigators cross-checked the database against the Swedish Population and Address Register for mortality. Kaplan-Meier survival estimates were calculated for the bariatric surgery group, control group, and reference group. The Gompertz proportional hazards regression model was used to compare mortality and life expectancy between patients in the control and surgery groups. Models were adjusted for demographic and clinical factors associated with premature mortality.

A total of 457 (22.8%) patients in the surgery group and 539 (26.4%) patients in the control group died during follow-up. Overall mortality was significantly lower in the surgery vs control group (HR, 0.77; 95% CI, 0.68-0.87; P <.001). This trend persisted in analyses stratified by cause of death; adjusted HRs for death from cardiovascular disease and cancer were 0.70 (95% CI, 0.57-0.85) and 0.77 (95% CI, 0.61-0.96), respectively.

The median life expectancy was 2.4 years (95% CI, 1.2-3.5) years longer in the surgery group vs the control group, with an adjusted difference of 3.0 years (95% CI, 1.8-4.2; P <.001). The median life expectancy was 7.4 years (95% CI, 5.4-9.4) longer in the reference cohort than in the control group (P <.001). The adjusted difference was 8.5 years (95% CI, 6.4-10.5; P <.001). In the surgery group, the median life expectancy was 5.5 years (95% CI, 3.4-7.6) shorter (adjusted difference) than in the reference cohort, or general population (P <.001). These data build on the investigators’ 2007 finding that bariatric surgery reduced overall mortality by 29% over a mean follow-up of 10.9 years.

Ninety-day mortality after bariatric surgery was 0.2%, according to the investigators. A total of 2.9% and 14.5% of patients in the surgery cohort required repeat surgery or experienced complications during the first 90 days, respectively.

“After an additional 13 years of follow-up, we now report that the difference in mortality persisted and that bariatric surgery was associated with a lower risk of death from both cardiovascular diseases and cancer. In addition, we show that life expectancy among patients with obesity who were given usual care was approximately 8 years shorter than in the general population, and this difference was decreased by bariatric surgery, which was associated with life expectancy that was approximately 3 years longer than that associated with usual care,” the study authors stated.

The primary limitations of the study were its non-randomized design and use of surgical techniques that are rarely used today. Further research is necessary to identify patients who may most benefit from bariatric surgery.

“Although many studies have shown that bariatric surgery is associated with a benefit with respect to the relative risk of death, our study, with its lengthy follow-up period, provides an estimate of life-years gained in association with surgery,” the investigators wrote. “In middle-aged patients with severe obesity, life expectancy was approximately 3 years longer among patients who underwent surgery than among those who received usual care.”

Disclosure: Two study authors declared affiliations with the pharmaceutical industry.

Please see the original reference for a full list of authors’ disclosures.

Reference

Carlsson LMS, Sjöholm K, Jacobson P, et al. Life expectancy after bariatric surgery in the Swedish Obese Subjects study. N Engl J Med. 2020;383:1535-1543. doi: 10.1056/NEJMoa2002449